The quote in the title of this post is drawn from this new Businessweek article headlined "Marijuana Law Mayhem Splits U.S. as Travelers Get Busted." Here is how the lengthy article gets started:

America is two nations when it comes to marijuana: in one it’s legal, in the other it’s not. The result is that people like B.J. Patel are going to jail. The 34-year-old Arizona man may face a decade in prison and deportation following an arrest in 2012. On a trip in a rented U-Haul to move his uncle from California to Ohio, he brought along some marijuana, which is legal for medicinal use in his home state.

Headed eastbound on I-44 through Oklahoma, Patel was stopped for failing to signal by Rogers County Deputy Quint Tucker, just outside Tulsa. He was about to get off with a warning when Tucker spotted a medical marijuana card in his open wallet. “‘I see you have this card. Where’s the marijuana?’” Patel recalled Tucker asking him. “I very politely and truthfully told him, ‘I’ll show you where it is.’” That’s where things started to go bad for Patel. He now faces trial next month on a felony charge.

Possessing pot for recreational use is legal in Washington and Colorado, and allowed for medicinal purposes in 23 states. The other half of the country, which includes Oklahoma, largely prohibits any amount for any purpose.

While challenges may land the issue before the U.S. Supreme Court, what exists now is a legal checkerboard where unwitting motorists can change from law-abiding citizens to criminals as fast as they pass a state welcome sign. The difference is especially clear in states like Idaho. Surrounded on three sides by pot-friendly Washington, Oregon, Nevada and Montana, Idaho State Police seized three times as much marijuana this year as in all of 2011.

“The manner in which a person acquires the drug is not relevant,” Teresa Baker, an Idaho police spokeswoman, said. “This is important to know for those who may purchase it legally elsewhere, believing that it will be overlooked.”

James Siebe, a lawyer in Coeur d’Alene, put it another way: “Come on vacation, leave on probation.”